The present invention relates generally to location information systems, and more particularly to a location information system for a wireless communication device and a method therefor.
I. Federal Communications Commission Authority Over 911 Service.
In the United States of America, the Federal Communications Commission (FCC) regulates wireless telecommunications companies that provide wireless telecommunications services. Wireless telecommunications is a group of telecommunications services under the heading of commercial mobile radio service (CMRS), as defined by the FCC. CMRS includes cellular, personal communications services (PCS), mobile satellite services (MSS) and enhanced specialized mobile radio (ESMR). Presently, CMRS does not include other forms of xe2x80x9cwirelessxe2x80x9d communications such as paging and traditional dispatch. The FCC""s authority over the wireless industry includes licensing, certain technical aspects of wireless service, timeframes in which service must be made available in given areas, and the provision of the 911 emergency answering service (i.e., 911 service), including basic 911 and enhanced 911 (i.e., E911).
The Department of Revenue of Washington State, USA provides an excellent summary of wireline and wireless 911 service in their document entitled: xe2x80x9cEnhanced 911 Funding Study.xe2x80x9d This study is presently located at the Internet web site: http://dor.wa.gov/index.asp?/pub/e911. The most relevant sections, including the executive summary, the introduction, chapter 1, chapter 2 text and drawings, and chapter 3 text and chart, have been printed out and provided with an information disclosure statement for the present patent application as a permanent reference to the present patent application. Chapter 1 describes the background of E911 wireless in Washington State. Chapter 2 describes E911 wireless technology with drawings. Chapter 3 describes the technical components of Phase I and II of E911 wireless with a chart. This entire study, including, but not limited to chapters 1, 2 and 3 along with the referenced drawings and charts, is herein incorporated into the present patent application by reference not only as a description for the background of the present invention, but also as a description for the detailed description of the present invention. Further, anything disclosed in this study, such as any term, concept, feature, service, drawing, chart, method, apparatus, system, etc. or portion thereof, may be used in combination with anything disclosed in the present patent application for support of any claims in the present or related patent applications. Highlights of this funding study are included in sections A through L, as follows.
A. General description of the 911 service.
To the public, 911 is an emergency telephone number that a caller dials for fire, medical, and/or police emergency assistance. Callers use both wireline and wireless phones to dial 911. Technically, 911 is an emergency answering service. When a caller dials the digits 9-1-1, a call travels over the public telephone network to a telecommunications company""s switch. The switch recognizes the 911 digits and sends the call to a 911 emergency answering center, commonly known as a public safety answering point (PSAP).
B. Types of 911 service.
There are two types of 911 servicexe2x80x94basic (basic 911) and enhanced (E911). With the basic 911 service, all 911 calls go to the same PSAP in a particular area even if the caller does not live in the area served by the PSAP. When the call taker answers the call, only the voice of the caller is provided. Therefore, the call taker must request the address information from the caller, and then determine which police, fire, and emergency medical agencies need to respond to the caller""s address. In addition, if the caller is unable to speak due to a medical circumstance such as a heart attack or choking, or does not know their phone number or location, the call taker may not be able to provide assistance to the caller.
With the E911 service, the telephone company switch routes the 911 call to the PSAP that serves the address of the location of the caller making the call. The telephone subscriber""s name (personal or business), the location of the telephone used by a caller, the telephone number, and associated emergency response information is sent to a computer display at a call taker""s answering position at the PSAP. The call taker has the information needed to send help to callers who are unable to speak or do not know their telephone number or location. The display of the telephone subscriber""s phone number is known as Automatic Number Identification (ANI). The display of the telephone subscriber""s location is known as Automatic Location Identification (ALI).
C. Current wireline and wireless 911 service.
Wireline 911 calls travel via a wireline E911 system from the caller to the PSAP. Wireless 911 calls travel via the wireless network to the wireline E911 system and then to the PSAP. The major components of the E911 wireline system are: a Public Switched Telephone Network (PSTN), a wireless telecommunications network, a dedicated E911 system, a E911 selective router, a E911 database, and the PSAPs. The PSTN is a wireline network of equipment, lines and controls assembled to establish communications paths between calling and called parties in North America. The wireless telecommunications network includes the radio frequencies, cell sites, equipment and controls that are assembled to transport a wireless call from a wireless phone to the PSTN. The dedicated E911 system includes network, database, and the specialized E911 equipment at the PSAP that is required to display the E911 caller""s phone number and location. The dedicated E911 system includes communication paths, known as telephone trunks, between wireline central office switches, or between a 911 control office and the PSAP that are used only for 911 calls. The E911 selective router is a piece of equipment located at the wireline telephone company""s regional switch. The selective router sends the E911 call to the proper PSAP based on the telephone number of the calling party, the location of the caller, and a routing code called an emergency service number (ESN). The ESN is a number representing emergency services agencies, such as law enforcement, fire, and emergency medical service, that serve a specific range of addresses within a particular geographic area known as an emergency service zone (ESZ). The ESN facilitates selective routing to the appropriate PSAP and the dispatching of the proper service agency(ies). It controls delivery of the voice call with the ANI to the PSAP and provides selective routing, speed calling, selective transfer, fixed transfer and certain maintenance functions for each PSAP. The E911 database is a database which houses the ANI and ALI records of telephone subscribers. The information includes a database of street names and house number ranges, and the telephone customer""s names, addresses, phone numbers and emergency response information. The 911 database is maintained by the telephone company. The PSAPs, also known as 911 call answering points, are facilities that are equipped and staffed to handle 911 calls twenty four hours a day, seven days a week. A primary PSAP receives the calls directly. A secondary PSAP only receives calls that have been transferred to them by the primary PSAP.
D. Operation Of The Present Wireline Enhanced 911 Service.
When a caller dials 9-1-1 from a wireline phone, the call travels over the PSTN just like any other call to the telephone company""s central office (CO). At the CO, the switching equipment recognizes the digits 9-1-1 and immediately transfers the call from the public switched network to dedicated 911 trunks that carry the call to the 911 selective router. At the 911 selective router, specialized software recognizes the 911 routing number associated with the caller""s telephone number and routes the call along dedicated 911 trunks to the PSAP that serves the caller""s geographic area. When the 911 call is received by the specialized 911 equipment at the PSAP, the caller""s phone number is automatically sent via dedicated data circuits to the 911 database, which is maintained by the telephone company providing 911 service to the PSAP. The caller""s name, address, telephone number, and associated emergency response information is retrieved from the 911 database. The caller""s information is sent to the PSAP over the data circuits to a display at the call taker answering position. The call taker has the information needed to send help to people who are unable to speak or do not know their telephone number or location.
E. Operation Of The Present Wireless 911 Service.
When a caller dials 911 from a wireless phone, the call travels via radio frequency (RF) to a base station, then to a switch and then to the PSTN telephone lines. The RF coverage area of the base station is known as a cell site. A cell site typically has one to three cell sectors. Each cell sector is an area geographically defined for RF coverage by the wireless company and served by one face of a cell antenna. Each cell site routes 911 calls to a predetermined PSAP that provides 911 service for the majority of the cell site. From this point, there are a variety of methods being used to transport the 911 calls to PSAPs including: forward the 911 call to a seven-digit number, forward the 911 call to a seven-digit 911 trunk number, seven-digit ANI and ten-digit ANI, as are well known in the telecommunications field.
F. E911 Service For Wireless Telecommunications.
The FCC issued an order in 1996 (docket number 94-102) that requires wireless carriers to provide E911 service to their subscribers. This means that wireless callers will have similar levels of ANI and ALI service for 911 calls as wireline callers currently have.
The wireless carriers are to implement wireless E911 in two phases (Phase I and II). In Phase I, they are required to provide the 911 caller""s phone number and cell sector location by April 1998 or six months after the service is ordered. In Phase II, the wireless carriers have to provide the caller""s latitude and longitude within a radius of 125 meters (410 feet) at least 67 percent of the time by Oct. 1, 2001 or six months after the service is ordered. This means that the actual location of the caller has to be determined, the data has to be sent through the 911 system to the PSAP, and the latitude and longitude data have to be converted into a usable location so the 911 call can be dispatched. If the caller is moving, it may be desirable that the location be updated to track the caller, although this is not a requirement of the FCC order. If the caller is out of their home area, the wireless systems have to be interoperable to offer 911 service.
G. Technical Challenges Of Implementing E911 Service For Phase II.
Locating the wireless caller. Wireless callers are usually mobile and technology has to locate callers in terms of latitude and longitude.
Generating accurate data to describe the location. Data for latitude, longitude, altitude, speed, and direction are necessary to physically locate a moving caller. Data calculations may be skewed by physical terrain, weather, user operation (e.g. indoor, in-vehicle, mobile or stationary). The time to transmit the data is affected by the call volume, geography, and user operation.
Moving the location data through the 911 network. The new data requires up to 40 digits. The current selective router and 911 network can only handle 8 digits.
Transmitting more data per caller through the system if the caller is moving. The data changes as the person moves. Data may need to be transmitted more frequently to effectively track a moving caller. This could result in conversations being interrupted if location updates use in-band signaling. In-band signaling means that the data and the voice travel on the same path to complete the call.
Translating digital data to a usable location. In order for call takers to communicate the actual location of a caller to dispatchers, existing maps will have to be corrected to reflect latitude and longitude and will need frequent updates to maintain accuracy. These maps will have to be electronically available at each call taker position at the PSAPs.
Interfacing with different frequency technologies and multiple infrastructure and network configurations. There are different technologies, frequencies, and network configurations among the wireless carriers. All of these systems have to interface with the E911 network.
H. Technical Solutions For Implementing E911 Service For Phase II.
Private research and development companies are currently developing and testing cellular network-based solutions and handset-based solutions for Phase II. With the cellular network solutions, location technology is added to the current cell sites to calculate a caller""s latitude and longitude. The technology works as long as the caller""s phone can access at least two cell sites. TruePosition has operated field trials for a cellular network solution along a 350 square mile area on Interstate 95 in New Jersey and in metropolitan Houston, Tex.
With the handset-based solutions, a Global Positioning System (GPS) receiver in the handset receives latitude and longitude data from twenty four GPS satellites orbiting the earth by and sends the data to the PSAP. This handset-based solution works as long as the GPS receiver can receive the satellite signal. Some handset-based solutions using the GPS receiver process the received location data in the handset and send the processed data through to the PSAP. Other handset-based solutions using the GPS receiver receive the location data in the handset and send the location data to a central location for processing. The processed location data is then sent to the PSAP. Integrated Data Communications (IDC) of Seattle, Wash. has technology that allows GPS location data to be processed by a GPS receiver in the wireless handset and then sent to the PSAP.
I. Operation Of Cellular Network-Based Solutions.
Cellular network-based solutions add location technology to the cell sites and calculate the location information using triangulation methods. When the caller dials 911, the signal is received up by two or more cell sites. Computer software analyzes data from the cell sites using a particular method or a hybrid of the following methods-time difference of arrival (TDOA) and angle of arrival (AOA). Examples of a cellular network-based solutions are disclosed in U.S. Pat. No. 5,890,068 (assigned to Cell-Loc, Inc.) and U.S. Pat. No. 5,963,866 (assigned to Lucent Technologies).
TDOA uses data from three or more cell sites and the time of arrival to compute where the caller is located. The TDOA system is an overlay system that fits on the existing network so there is little impact to the wireless network. Because the system relies exclusively on the radio signals that are broadcast from the telephone handset to locate a caller, the location quality of the system generally follows the voice quality of the underlying cellular network. As a wireless carrier expands and improves coverage in their network, the location system quality similarly expands. For a TDOA system, the location accuracy for indoor coverage deteriorates as the quality of the wireless call deteriorates. If the indoor cellular phone has good voice reception and transmission quality, then the location accuracy is relatively unaffected. Automatic location identification for TDOA includes latitude and longitude but not altitude.
The advantages to this method are that it can be applied to different wireless technologies and no modification to the handset is required. Once the system is installed all wireless subscribers would have automatic location identification within 410 feet 67 percent of the time as long as their wireless phone signal could access a cell site.
The challenges with TDOA are that it is dependent on the cell site configuration such as exact cell location, antenna height, and radio channel allocations. Therefore cooperation with existing wireless carriers is needed. It is also dependent on the number of TDOA receiver sites. The quality of accuracy of a TDOA system is proportional to the coverage area of TDOA receiver sites. An urban core typically requires one TDOA receiver site for every three or four cell sites. A rural area, with much larger cell coverage patterns, would typically require one TDOA receiver per cell site. The performance is affected when the radio signal bounces off objects along the path from the radio transmitter such as hills and buildings resulting in one strong signal and several identical weaker signals being received at different times. This phenomenon is known as multipath effect. The quality of the indoor coverage varies with the strength of the signal. TDOA requires accurate network time synchronization and an extensive cell site overlay.
AOA uses data from two or more cell sites and the angle of arrival to compute where a caller is located. The advantages to this method are that it applies to all mobile phones of any make, model, and vintage with no modifications to the handset required. The AOA system is an overlay system that fits on the existing network so there is little impact to the wireless network. Because the system relies exclusively on the radio signals that are broadcast from the phone to locate a caller, the location quality of the system generally follows the voice quality of the underlying cellular network. Similar to TDOA, the AOA system requires a series of angular receiver sites to be deployed in the network. There are fewer AOA receiver sites needed in an urban core per cell than in a rural area. An asset of AOA is its resistance to multipath effects which includes good indoor coverage. The challenges with this system are that it is typically dependent on additional antenna structures at the cell site. Therefore cooperation with the existing wireless operators is needed for access to most structures. The accuracy of an AOA system is inversely proportional to the distance of the phone from the AOA sites (the further the phone is away, the less accurate the system). Also, in rural configurations, cell sites tend to be adjacent to highways. This is a poor configuration for AOA since no location can be detected along the line-of-sight between two AOA receivers.
J. Operation Of Handset-Based Solutions.
Currently there are two handset solutions being tested. Both use Global Positioning Satellite (GPS) technology to obtain location information. Examples of the handset-based solutions are disclosed in U.S. Pat. No. 5,479,482 (assigned to ATandT, Corp.) and U.S. Pat. No. 5,388,147 (assigned to ATandT, Corp.). The advantage of a GPS solution is its inherent high accuracy (as close as 40 feet). Some of the challenges with this technology will be its use in skyscrapers, forming what is known as xe2x80x9curban canyonsxe2x80x9d or an electromagnetic shielding effect, where it is difficult for the handset to receive the GPS data. The Washington State funding study suggests that tall buildings can be retrofitted to receive GPS information. Antennae could be placed on the roof and at each floor of the building to send the signal to a GPS receiver inside the building. However, this suggestion does not disclose how a cellular telephone would receive GPS information from the GPS antenna and receiver, since the GPS antenna and GPS receiver are disclosed to be attached or in the building and not attached to, disposed in or communicating with the cellular telephone. Further, with this suggestion it appears that GPS receiver would only receive the locations of the GPS antennas because that is where the GPS data is collected from the GPS satellites. Moreover, in an urban canyon environment, it is possible that only the GPS antenna located on the top of the building will be able to receive the GPS signals because it is able to receive the GPS signals from the GPS satellites. The other GPS antenna located on each floor may also be shielded from the GPS signals from the GPS satellites by the building""s own structure if the GPS antennas are located inside the building or by other nearby tall skyscrapers if the GPS antennas are located outside of the building at each floor. Regardless of the handset-based solution, the handset solution needs to be accepted as a national solution or handsets of subscribers from different areas will not be compatible. There is also the issue of what to do about the handsets that are currently in use. One solution is to offer an after market battery pack adapter that allows the addition of the GPS receiver to the battery pack. Since there is a fairly fast turnover in handsets it would not be too long before a large number of users would have the GPS technology built into the handset.
K. Operation Of A Cellular Network-Assisted GPS Handset Solution.
The cellular network-assisted GPS uses a GPS receiver in the handset to collect raw data from the GPS satellites. The raw data is then sent to equipment located at cell sites and then forwarded to network equipment for further processing. This network equipment computes and sends the latitude, longitude, and other location information to other network equipment for transmission to the PSAP. The advantage of the cellular-assisted GPS is that it reduces the processing of satellite data in the handset by using high-speed network-based computing. An additional advantage is that error correction and the time to get an initial reading are improved by the ability of the network to send information to the handset.
L. Operation Of Autonomous GPS Handset Solution.
The autonomous GPS handset uses a complete GPS receiver and processor located in the handset. This stand-alone device does not need any network connections to obtain location information. The on-board processor can send location information through the cellular network overhead data channels or over the voice path via in-band technology. The advantage of sending the data via the voice path is that location information can be sent over any cellular or wireline network directly to the PSAP without changing any of the existing network.
M. Operation Of A Cellular Network-Based And Handset-Based Solution.
The cellular network-based solution, as described hereinabove in section I, and handset-based solution, as described hereinabove in sections J, K and L, may also be combined to provide a more accurate determination of the location of the cellular handset. An example of such a combination solution is disclosed in U.S. Pat. No. 5,724,660 (assigned to ATandT Wireless Services, Inc.).
II. Bluetooth
Bluetooth, presently having a web site at http://www.bluetooth.com, is a codename for an open technology standard specification jointly developed by Ericsson, Intel, IBM, Toshiba, and Nokia. Bluetooth is for small form factor, low-cost, short range radio links of voice and data communications between mobile devices, such as between a cellular phone and a laptop computer, and between mobile and fixed devices, such as between an electronic camera and a printer. The short range radio links are implemented using compact and cost effective short range radio transceivers operating in the international 2.4 GHz ISM band. Hence, Bluetooth replaces cables and makes automatic, unattended, short range communications between devices possible. However, Bluetooth does not appear to disclose or suggest an application for 911 service, including E911 service for wireless communication devices, such as cellular telephones.
Accordingly, there is a need for a location information system to provide location information, such as the ALI for the E911 service, for a wireless communication device, such as a cellular telephone, and a method therefor to permit the wireless communication device to engage the E911 service in places where the cellular network-based solutions, cellular handset-based solutions, or a combination of the cellular network-based solutions and the cellular handset-based do not adequately perform.